Corrosion Under Insulation (CUI)

Corrosion Under Insulation (CUI) is the hidden corrosion that develops on steel surfaces covered by thermal insulation or fireproofing. It is caused by trapped moisture, condensation, or chemical ingress beneath the insulation.

Where does CUI occur?

CUI is a critical issue in:

• Oil & Gas – offshore risers, flare booms, topside piping.
• Petrochemical & Chemical plants – process vessels, reactors, insulated pipelines.
• Marine & Offshore wind – deck areas, turbine towers, hull details.
• Power generation – boilers, turbines, and high-heat components.

For you as an operator, CUI is dangerous because it often remains undetected until severe metal loss or leaks occur.

Extra explanation

• Causes:
  • Moisture ingress from damaged insulation or poor sealing.
  • Condensation on cold surfaces.
  • Chemical-laden atmospheres accelerating hidden corrosion.

Consequences:

• Wall thinning and leaks.
• Unplanned shutdowns or safety incidents.
• Expensive insulation removal and reinstallation.

Standards such as API 570 and ISO 19277 provide guidelines for managing CUI.

Pinovo and CUI

Pinovo’s vacuum blasting helps tackle CUI by:

• Removing insulation locally and blasting the exposed steel dust-free.
• Operating in ATEX zones where many insulated lines are located.
• Enabling inspection by cleaning steel surfaces for UT thickness measurement.
• Allowing quick recoating to prevent further CUI progression.

Pinovo does not remove or reinstall insulation, but ensures CUI-affected steel is safely exposed, cleaned, and prepared for protective coating.